The present invention relates to a pattern transfer method and imprint device that pressurizes a stamper having concaves and convexes on the surface thereof and a transferred object and thus transfers the concaves and convexes of the stamper onto the surface of the transferred object.
In recent years, the reduction in size and higher integration have been progressing in integrated circuits, and as the pattern transfer technique for realizing the fine processing, higher precision of the photolithography apparatus has been pursued. However, the processing method is approaching the wavelength of a light source of light exposure and the lithography technology is also approaching the limit. For this reason, for the purpose of pursuing further reduction in size and higher precision, an electron beam lithography apparatus, which is a type of a charged particle beam apparatus, is used in place of the lithography technology.
As opposed to the one-shot exposure method in the pattern formation using a light source, such as an i line or an excimer laser, the pattern formation using an electron beam employs a method of drawing mask patterns, and therefore the more patterns to draw, the more exposure (drawing) time it takes and the more pattern formation time it takes, which is a disadvantage. For this reason, as the degree of reduction in pattern size and the degree of integration increase exponentially, the pattern formation time will also increase exponentially accordingly, and thus a significant degradation in throughput is a concern. Then, for the purpose of speeding up the electron beam exposure apparatus, a collective pattern irradiation method has been under development where various shapes of masks are combined and these masks are irradiated with an electron beam to thereby form an electron beam of a complicated shape. As a result, while the reduction in pattern size is progressed, the electron beam lithography apparatus is forced to be enlarged and in addition a mechanism to control the mask position with high accuracy is required, thus causing a disadvantage of increased apparatus cost.
On the other hand, there is an imprint technique for forming fine patterns at low cost. This is a technique, in which a stamper having concaves and convexes of the same pattern as the pattern desired to be formed on a substrate is die-pressed against the surface of a transferred object and then the stamper is detached to thereby transfer a predetermined pattern. Here, with this transferring, fine structure of 25 nm or less can be formed. Then, with regard to the imprint technique, applications to the recording bit formation of a large-capacity recording medium, the pattern formation of semiconductor integrated circuits, and the like are being studied.
In the imprint technique, when forming a fine pattern on the substrate of a large-capacity recording medium or on the substrate of a semiconductor integrated circuit, a relative position between a stamper and a transferred object needs to be aligned with high accuracy in prior to die-pressing the stamper against a resin film layer formed on the surface of the transferred object. For example, JP-A-2005-116978 discloses a technique, in which an alignment mark is provided in the surface of a stamper and the surface of a transferred object, respectively, and then the respective alignment marks of the stamper and transferred object are observed using an optical method, thereby aligning the relative position between the stamper and the transferred object.
However, the alignment mark needs to be provided in both the stamper and transferred object, and thus, it may be difficult to provide the alignment mark in the transferred object, as in a disc substrate used for a magnetic recording medium, for example.
As a method of making alignment of a disc substrate used for a magnetic recording medium without providing an alignment mark in the transferred object, for example, there is known an approach of mechanically making alignment by passing an alignment pin through a central hole of the disc substrate, as in U.S. Pat. No. 6,757,116B1. However, because the alignment accuracy will depend on the processing accuracy between the central hole and the pin, the alignment accuracy obtained in the disc substrate used for a magnetic recording medium is 30 μm at best, and it is thus difficult to make high precision alignment. Moreover, because the pin will mechanically contact with the disc substrate or the stamper, the pin tends to damage the contact portion, resulting in damaging the disc substrate or the stamper.
On the other hand, as the method of aligning a substrate with an exposure stage in an exposure apparatus, there is known an approach to detect the shape of the substrate and the information on the center position from the position information on the substrate edge (JP-A-2001-264015). However, applications to the stamper of imprint technique and to the alignment of the transferred object are not disclosed at all.